Flame-cut detecting device for internal combustion engine

ABSTRACT

When operating area detecting means detects an operating area that has a predetermined rotation number of below, flame-cut determination selecting means determines the flame-cut on the basis of the logical product between a detection result of first flame-cut detecting means and a detection result of second flame-cut detecting means.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a flame-cut detecting device foran internal combustion engine, and more particularly to a flame-cutdetecting device for an internal combustion engine having enhancedreliability in the entire operating area by detecting a flame-cut on thebasis of the rotation information or an ion current in an operatingarea.

[0002] Conventionally, the flame-cut detecting device for the internalcombustion engine employing a variation in pulse period ratio as therotation information was well known. Further, the flame-cut detectingdevice for the internal combustion engine employing a detection level ofthe ion current was also well known.

[0003] Generally, it is well known that the reliability (S/N ratio) offlame-cut detection based on the rotation information and the ioncurrent changes in accordance with the operating area (rotation number)of the internal combustion engine, and the reliability of flame-cutdetermination based on the period ratio (rotation information) isdegraded with an increased rotation number of the engine. Also, thereliability of flame-cut determination based on the ion current isdegraded with a decreased rotation number of the engine.

[0004] Thus, in order to solve the above-mentioned problems, a techniquehas been proposed in which the reliability of flame-cut determination inthe entire operating area is improved by detecting a flame-cut on thebasis of the rotation information in a low rotation area and detectingthe flame-cut on the basis of the ion current in a high rotation area,as disclosed in the Unexamined Japanese Patent Application PublicationNo. 2000-240550.

[0005] However, in a multiple cylinder engine (e.g., 8 or greatercylinder engine), the reliability of flame-cut determination in the lowrotation area may be degraded even on the basis of the rotationinformation. In the conventional flame-cut detecting device for theinternal combustion engine as above mentioned, the flame-cut detectionis only based on the rotation information in the low rotation area,resulting in a problem that the reliability of flame-cut determinationis degraded to lead to a false determination of flame-cut during thenormal combustion.

SUMMARY OF THE INVENTION

[0006] This invention is achieved to solve the above-mentioned problem,and it is an object of the invention to provide a flame-cut detectingdevice for the internal combustion engine in which the reliability offlame-cut determination in the low rotation area is improved.

[0007] According to a first aspect of the present invention, there isprovided a flame-cut detecting device for an internal combustion enginecomprising various kinds of sensors for sensing an operating conditionof the internal combustion engine, operating area detecting means fordetecting the operating area of the internal combustion engine from theoperating condition, control parameter calculating means for calculatinga control parameter of the internal combustion engine, on the basis ofthe operating condition, an igniter for igniting the internal combustionengine in accordance with the control parameter, an ion current detectorfor detecting an ion current produced by ignition of the internalcombustion engine, first flame-cut determination means for determining aflame-cut of the internal combustion engine on the basis of a temporalchange of the rotation information of the internal combustion enginecontained in the operating condition, second flame-cut determinationmeans for determining a flame-cut of the internal combustion engine onthe basis of the ion current, and flame-cut determination selectingmeans for selectively employing the first or second flame-cutdetermination means in accordance with the operating area, characterizedin that when the operating area detecting means detects the operatingarea that is less than or equal to a predetermined rotation number, theflame-cut determination selecting means determines the flame-cut inaccordance with the logical product between a detection result of thefirst flame-cut detecting means and a detection result of the secondflame-cut detecting means.

[0008] Also, according to a second aspect of the invention, there isprovided the flame-cut detecting device for the internal combustionengine, characterized in that the flame-cut determination selectingmeans comprises ion current state determining means for determining anaptitude state of the ion current, wherein when it is determined thatthe ion current is aptitude, means for determining the flame-cut inaccordance with the logical product between a detection result of thefirst flame-cut detecting means and a detection result of the secondflame-cut detecting means is employed in an area of a predeterminedrotation number or less, while when it is determined that the ioncurrent is inaptitude, the first flame-cut detecting means is employedin the area of the predetermined rotation number or less.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1

[0010]FIG. 1 is a block diagram showing a flame-cut detecting device foran internal combustion engine according to an embodiment 1 of thepresent invention.

[0011]FIG. 2

[0012]FIG. 2 is a graphical representation for explaining an operatingarea for the flame-cut detecting device for the internal combustionengine according to the embodiment 1 of the invention.

[0013]FIG. 3

[0014]FIG. 3 is a waveform diagram showing an operation of determiningthe ion current state in the flame-cut detecting device for the internalcombustion engine according to the embodiment 1 of the invention.

[0015]FIG. 4

[0016]FIG. 4 is a flowchart showing the processing operation of theflame-cut detecting device for the internal combustion engine accordingto the embodiment 1 of the invention.

[0017]FIG. 5

[0018]FIG. 5 is an explanatory table for explaining means fordetermining the flame-cut in accordance with the logical product betweenthe determination result of the rotation information and thedetermination result of the ion current in the flame-cut detectingdevice for the internal combustion engine according to the embodiment 1of the invention.

[0019]FIG. 6

[0020]FIG. 6 is a flowchart showing the processing operation of aflame-cut detecting device for an internal combustion engine accordingto an embodiment 2 of the invention.

DETAILED DESCRIPTION OF THE PREFEREED EMBODIMENTS Embodiment 1

[0021]FIG. 1 is a block diagram showing a flame-cut detecting device foran internal combustion engine according to an embodiment 1 of theinvention. FIG. 2 is a graphical representation for explaining anoperating area detected by operating area detecting means as shown inFIG. 1. And FIG. 3 is a waveform diagram showing the operation of ioncurrent state determining means contained in flame-cut determinationselecting means as shown in FIG. 1.

[0022] In FIG. 1, an engine (not shown) is provided with a rotationsensor land an air flow sensor 2 as a variety of kinds of sensors tosense the operating condition, an injector 3 for injecting a fuel as anactuator for driving the engine, and an igniter 4 for controlling theignition.

[0023] Herein, as a variety of kinds of sensors, the rotation sensor 1and the air flow sensor 2 are only shown, but practically, a throttleaperture sensor and a coolant temperature sensor may be provided asother kinds of sensors, not shown. Also, as the actuator for driving theengine, the injector 3 and the igniter 4 are shown, but practically anISC valve actuator may be provided in a bypass line of a suction pipe asother actuators, not shown.

[0024] The rotation sensor 1 outputs a pulse signal corresponding to theengine rotation number Ne (rotation information). This pulse signal hasan edge corresponding to each reference crank angle of a multiple enginecylinder, and each reference crank angle is employed to calculate thecontrol timing of the engine. The air flow sensor 2 outputs a voltagesignal corresponding to a suction amount Qa of the engine. Also, theigniter 4 is provided with an ion current detection unit 5 for detectingan ion current i produced at the time of ignition to output an ioncurrent detection signal D.

[0025] An ECU (Electronic Control Unit) 10 consisting of a microcomputertakes in a sensor signal indicating the engine rotation number Ne andthe suction amount Qa and an ion current detection signal D, forexample, as the operating condition of the engine, to make the flame-cutdetermination (hereinafter described), and as a result, outputs aflame-cut determination signal E to a failure indicator 6. Also, the ECU10 outputs a fuel injection signal J to the injector 3 and an ignitionsignal P to the igniter 4.

[0026] The ECU 10 comprises control parameter calculating means 11 andoperating area detecting means 12 into which the engine rotation numberNe and the suction amount Qa are entered, first flame-cut determiningmeans 15 composed of period ratio calculating means 13 and comparisonmeans 14, into which the engine rotation number Ne is entered, secondflame-cut determining means 16 into which the ion current detectionsignal D is entered, and flame-cut determination selecting means 17 intowhich the determination results of the first and second flame-cutdetermining means 15 and 16 are entered.

[0027] The control parameter calculating means 11 calculates the controlparameters (a fuel injection signal J and an ignition signal P) of theengine, on the basis of the operating condition (engine rotation numberNe and suction amount Qa). The fuel injection signal J and the ignitionsignal P are output as the drive signals for the injector 3 and theigniter 4, respectively.

[0028] The operating area detecting means 12 detects a plurality ofoperating areas A and B divided as shown in FIG. 2 from the enginerotation number Ne, and outputs an operating area detection signal Rindicating each of the operating areas A and B.

[0029] In FIG. 2, the engine rotation number Ne (rpm) is representedalong the transverse axis, and the engine load CE is represented alongthe longitudinal axis. The operating area A denotes a low rotation areawith a rotation number of 1500 rpm or less corresponding to an idlerotation number, and the operating area B denotes a high rotation areawith a rotation number of over 1500 rpm. Each of the operating areas Aand B may be variably set in accordance with the engine load CE (suctionamount Qa) as indicated by the broken line in FIG. 2.

[0030] The period ratio calculating means within the first flame-cutdetermining means 15 calculates the preceding and succeeding periodratios by measuring successively the period of edge (reference crankangle) of a pulse signal indicating the engine rotation number Ne, andstores successively the temporal change of the period ratio. Also, thecomparison means 14 within the first flame-cut determining means 15compares a change in the period ratio with a predetermined value, andoutputs a first flame-cut determination signal E1 if a rapid decrease inthe engine rotation number Ne (flame-cut) is determined.

[0031] The second flame-cut determining means 16 determines thecombustion condition at the time of ignition from a peak level of theion current detection signal D or an integral value of the ion currentdetection signal D during a predetermined interval after ignition, forexample, and determines the flame-cut of the engine to output a secondflame-cut determination signal E2 if the peak level of the ion currentdetection signal D or the integral value is less than or equal to areference value.

[0032] The flame-cut determination selecting means 17 employsselectively the first or second flame-cut determining means 15 or 16 inaccordance with the operating area detection signal R to output thefirst flame-cut determination signal E1 or the second flame-cutdetermination signal E2, or the logical product between the firstflame-cut determination signal E1 and the second flame-cut determinationsignal E2, as a final flame-cut determination signal E, to the controlparameter calculating means 11 and the failure indicator 6.

[0033] Thereby, the control parameter calculating means 11 preventsaggravation of the exhaust gas and the damage on the engine bycorrecting the output timing of the fuel injection signal J and theignition signal P in response to a flame-cut determination signal E.Also, the failure indicator 6 displays the presence or absence of afailure due to flame-cut in response to a flame-cut determination signalE.

[0034] The flame-cut determination selecting means 17 uses the firstflame-cut determining means 15 based on the engine rotation number Neand the second flame-cut determining means 16 based on the ion currentto output the logical product of these flame-cut determination signalsas a final flame-cut determination signal E, if the operating areadetection signal R indicates the operating area A (low rotation area),as shown in FIG. 5.

[0035] Also, the flame-cut determination selecting means 17 uses thesecond flame-cut determining means 16 based on the ion current that isreliable in the high rotation side to output the second flame-cutdetermination signal E2 as a final flame-cut determination signal E, ifthe operating area detection signal R indicates the operating area B(high rotation area).

[0036] Moreover, the flame-cut determination selecting means 17comprises ion current state determining means (not shown) fordetermining the aptitude state of ion current i, and disables the secondflame-cut determining means 16 in the operating area B and enables thefirst flame-cut determining means 15 alone, if it is determined that theion current i is inaptitude.

[0037] The ion current state determining means within the flame-cutdetermination selecting means 17 determines the inaptitude state of theion current i, and sets a flag F (F=1) indicating that the ion currentis inaptitude, if the peak level Dp of the ion current detection signalD is less than or equal to a predetermined value Dr, as shown in FIG. 3,for example.

[0038] At this time, the inaptitude state of ion current i can bedetermined relatively simply only by comparing the peak level Dp with apredetermined value Dr. Also, the predetermined value Dr is set to avalue greater than the reference value for determining the flame-cut.

[0039] In FIG. 3, since the noise DN at the time of ignition issuperposed on the ion current detection signal D, the ion current statedetermining means masks an interval immediately after ignition with amask signal and detects the ion current detection signal D with adetermination signal after completion of the mask signal to have adetermination interval T to prevent the false detection of ignitionnoise DN.

[0040] The operation will be now described. FIG. 4 is a flowchartshowing the operation of the flame-cut detecting device for the internalcombustion engine according to the embodiment 1 of this invention,namely, the processing operation for the operating area detecting means12 and the flame-cut determination selecting means 17 within the ECU 10.

[0041] First of all, the ion current state determining means within theflame-cut determination selecting means 17 determines the state of ioncurrent i (step S1). That is, whether or not the ion current i isaptitude is determined depending on whether or not the peak level Dp ofthe ion current detection signal D is less than or equal to thepredetermined value Dr (step S2).

[0042] If it is determined that Dp is less than or equal to Dr (i.e.,YES), the ion current i is in inaptitude state, the flag F is set to “1”(step S3), and the procedure goes to step S5.

[0043] Also, if it is determined that Dp is greater than Dr (i.e., NO)at step S2, the ion current i is in aptitude state, whereby the flag Fis cleared to “0” (step S4), and the procedure goes to step S5.

[0044] The operating area detecting means 12 detects the engine rotationnumber Ne on the basis of an output signal of the rotation sensor 1(step S5), and it is determined whether or not the engine rotationnumber Ne is less than or equal to a predetermined rotation number Ne1(e.g., 1500 rpm) (operating area A) (step S6).

[0045] If it is determined that Ne is less than or equal to Ne1 (i.e.,YES), the operating area detecting means 12 outputs an operating areadetection signal R indicating the operating area A. In response to that,the flame-cut determination selecting means 17 selects means fordetermining the flame-cut, using the logical product between the firstflame-cut determination signal E1 and the second flame-cut determinationsignal E2 (step S7), and determines the presence or absence offlame-cut, using the logical product between the first flame-cutdetermination signal E1 and the second flame-cut determination signal E2(step S11). After the end of the processing of FIG. 4, the procedurereturns.

[0046] If it is determined that Ne is greater than Ne1 (i.e., NO) atstep S6, the operating area detecting means 12 outputs an operating areadetection signal R indicating the operating area B. In response to that,the flame-cut determination selecting means 17 determines whether or notthe flag F indicating the inaptitude of ion current is “1” (step S8).

[0047] If it is determined that the flag F is equal to 0 (i.e., NO), thesecond flame-cut determining means 16 is selected (step S10) because theion current i is in aptitude state, and then the presence or absence offlame-cut is determined using the second flame-cut determination signalE2 (step S11). After the end of processing of FIG. 4, the procedurereturns.

[0048] If it is determined that the flag F is equal to 1 (i.e., YES) atstep S8, the flame-cut determination selecting means 17 disables theselected second flame-cut determining means 16, and selects the firstflame-cut determining means 15 (step S9), and then the presence orabsence of flame-cut is determined employing the first flame-cutdetermination signal E1 (step S11). After the end of processing of FIG.4, the procedure returns.

[0049] As described above, with the embodiment 1 of the invention, theflame-cut determination selecting means 17 employs means for determiningthe flame-cut in accordance with the logical product between thedetection result of the first flame-cut determining means 15 based onthe rotation information and the detection result of the secondflame-cut determining means 16 based on the ion current in the operatingarea A. That is, in an area of a predetermined rotation number or less,the flame-cut is determined only if both the detection result of therotation information and the detection result of the ion currentindicate the flame-cut. Also, in the operating area B, the secondflame-cut determining means 16 is employed if the ion current state isaptitude, or the first flame-cut determining means 15 is employed if itis inaptitude.

[0050] Thereby, the flame-cut can be detected with high reliability inall the operating areas A and B. In particular, the reliability offlame-cut determination in the low rotation area can be improved. Also,even if the waveform and level of the ion current detection signal D ischanged due to a difference in the fuel properties so that the ioncurrent i is in inaptitude state, a false detection of flame-cut can beprevented by disabling the second flame-cut determining means 16 in theoperating area B and changing to the first flame-cut determining means15.

Embodiment 2

[0051]FIG. 6 is a flowchart showing the operation of the flame-cutdetecting device for the internal combustion engine according to anembodiment 2 of this invention. In the same figure, step S21 to step S26correspond to step S1 to step S6 in the operation flowchart of theembodiment 1, and the detailed explanation of step S21 to step S26 isomitted.

[0052] If it is determined that Ne is less than or equal to Ne1 (i.e.,YES) at step S26, the operating area detecting means 12 outputs anoperating area detection signal R indicating the operating area A. Inresponse to that, the flame-cut determination selecting means 17determines whether or not the flag F indicating the inaptitude of ioncurrent is “1” (step S27).

[0053] If it is determined that the flag F is equal to 0 (i.e., NO), themeans for determining the flame-cut is selected using the logicalproduct between the first flame-cut determination signal E1 and thesecond flame-cut determination signal E2 (step S28), and then thepresence or absence of flame-cut is determined using the logical productbetween the first flame-cut determination signal E1 and the secondflame-cut determination signal E2 (step S32). After the end ofprocessing of FIG. 6, the procedure returns.

[0054] If it is determined that the flag F is equal to 1 (i.e., YES) atstep S27, the flame-cut determination selecting means 17 disables theselected second flame-cut determining means 16, and selects the firstflame-cut determining means 15 (step S29), and then the presence orabsence of flame-cut is determined employing the first flame-cutdetermination signal E1 (step S32). After the end of processing of FIG.6, the procedure returns.

[0055] If it is determined that Ne is greater than Ne1 (i.e., NO) atstep S26, the operating area detecting means 12 outputs an operatingarea detection signal R indicating the operating area B. In response tothat, the flame-cut determination selecting means 17 determines whetheror not the flag F indicating the inaptitude of ion current is “1” (stepS30) If it is determined that the flag F is equal to 0 (i.e., NO), thesecond flame-cut determining means 16 is selected (step S31) because theion current i is in aptitude state, and then the presence or absence offlame-cut is determined using the second flame-cut determination signalE2 (step S32). After the end of processing of FIG. 6, the procedurereturns.

[0056] If it is determined that the flag F is equal to 1 (i.e., YES) atstep S30, the flame-cut determination selecting means 17 disables theselected second flame-cut determining means 16, and selects the firstflame-cut determining means 15 (step S29), and then the presence orabsence of flame-cut is determined employing the first flame-cutdetermination signal E1 (step S32). After the end of processing of FIG.6, the procedure returns.

[0057] As described above, with the embodiment 2 of the invention, theflame-cut determination selecting means 17 employs means for determiningthe flame-cut in accordance with the logical product between thedetection result of the first flame-cut determining means 15 based onthe rotation information and the detection result of the secondflame-cut determining means 16 based on the ion current, if the ioncurrent state is aptitude in the operating area A, or the firstflame-cut determining means 15 if it is inaptitude.

[0058] That is, in the case where the ion current is determined to beaptitude in an area of a predetermined rotation number or less by theion current state determining means, the flame-cut is determined only ifboth the detection result of the rotation information and the detectionresult of the ion current indicate the flame-cut, or in the case wherethe ion current is determined to be inaptitude, the flame-cut isdetermined with the detection result of the rotation information.

[0059] Thereby, even if the waveform and level of the ion currentdetection signal D is changed due to a difference in the fuel propertiesso that the ion current i is in inaptitude state, a false detection offlame-cut can be prevented by disabling the second flame-cut determiningmeans 16 in the operating area A and changing to the first flame-cutdetermining means 15. The control can be made at higher precision thanin the embodiment 1.

[0060] As described above, according to the first aspect of the presentinvention, there is provided a flame-cut detecting device for aninternal combustion engine comprising various kinds of sensors forsensing an operating condition of the internal combustion engine,operating area detecting means for detecting the operating area of theinternal combustion engine from the operating condition, controlparameter calculating means for calculating a control parameter of theinternal combustion engine, on the basis of the operating condition, anigniter for igniting the internal combustion engine in accordance withthe control parameter, an ion current detector for detecting an ioncurrent produced by ignition of the internal combustion engine, firstflame-cut determination means for determining a flame-cut of theinternal combustion engine on the basis of a temporal change of therotation information of the internal combustion engine contained in theoperating condition, second flame-cut determination means fordetermining a flame-cut of the internal combustion engine on the basisof the ion current, and flame-cut determination selecting means forselectively employing the first or second flame-cut determination meansin accordance with the operating area, characterized in that when theoperating area detecting means detects the operating area that is lessthan or equal to a predetermined rotation number, the flame-cutdetermination selecting means determines the flame-cut in accordancewith the logical product between a detection result of the firstflame-cut detecting means and a detection result of the second flame-cutdetecting means, whereby there is the effect that the flame-cutdetecting device for internal combustion engine with improvedreliability of determining the flame-cut in the low rotation area isprovided.

[0061] Also, according to the second aspect of the invention, there isprovided the flame-cut detecting device for the internal combustionengine, characterized in that the flame-cut determination selectingmeans comprises ion current state determining means for determining anaptitude state of the ion current, wherein when it is determined thatthe ion current is aptitude, means for determining the flame-cut inaccordance with the logical product between a detection result of thefirst flame-cut detecting means and a detection result of the secondflame-cut detecting means is employed in an area of a predeterminedrotation number or less, while when it is determined that the ioncurrent is inaptitude, the first flame-cut detecting means is employedin the area of the predetermined rotation number or less, whereby thereis the effect that the flame-cut detecting device for internalcombustion engine is provided in which the reliability of determiningthe flame-cut in the low rotation area is improved and the falsedetection flame-cut is prevented even when the ion current is unstable.

What is claimed is:
 1. A flame-cut detecting device for an internalcombustion engine comprising: sensors for sensing an operating conditionof said internal combustion engine, operating area detecting means fordetecting a divided operating area, on the basis of the rotationinformation of said internal combustion engine, control parametercalculating means for calculating a control parameter of said internalcombustion engine, on the basis of the operating condition sensed bysaid sensors, an igniter for igniting said internal combustion engine inaccordance with the control parameter, an ion current detector fordetecting an ion current produced by ignition of said internalcombustion engine, a first flame-cut determination means for determininga flame-cut of said internal combustion engine on the basis of atemporal change of the rotation information of said internal combustionengine contained in the operating condition sensed by said sensors, asecond flame-cut determination means for determining a flame-cut of saidinternal combustion engine on the basis of the ion current, andflame-cut determination selecting means for selectively employing saidfirst or second flame-cut determination means in accordance with theoperating area, wherein when said operating area detecting means detectsthe operating area that is less than or equal to a predeterminedrotation number, said flame-cut determination selecting means determinesthe flame-cut in accordance with a logical product between a detectionresult of said first flame-cut detecting means and a detection result ofsaid second flame-cut detecting means.
 2. The flame-cut detecting devicefor the internal combustion engine according to claim 1, wherein saidflame-cut determination selecting means comprises: ion current statedetermining means for determining an aptitude state of an ion current,and wherein when it is determined that the ion current is aptitude, theflame-cut is determined in accordance with the logical product between adetection result of said first flame-cut detecting means and a detectionresult of said second flame-cut detecting means in an area of apredetermined rotation number or less, and when it is determined thatthe ion current is inaptitude, said first flame-cut detecting means isemployed in said area of the predetermined rotation number or less.